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Post by kwarkgebak on Feb 12, 2021 12:19:51 GMT
From time to time, a hum is heard in my right speaker. When I fiddle the cable a little, the hum is gone most times. So I should be able to solve this by just replacing the cable, but where's the fun in that?  The thing is, when I switch the speaker off and on again, the hum is gone too. Now this makes me curious. Why does the hum disappear when I do this? Config: MOTU Ultralite mk3 outs to Nanopatch volumecontroller to Samson subwoofer. Then unbalanced rca out to Adam A7x speakers. |
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Post by rock on Feb 12, 2021 16:02:50 GMT
I'm guessing you are fiddling with the AC power cable? Even though it's not that much fun switching a cable, if it fixes the problem, you probably should give it a go.
If in the cable, it is an intermittent open earth wire or probably more unlikely, an intermittent short from earth to neutral, you can test with a continuity tester. The ones with a tone will give you an instantaneous indication as you fiddle with the cable under test.
About ground loops, here's a story about how I eventually found one in my systems:
I have my "Band Rehearsal/Jamming PA, recording set up including computer, interface, mixer, outboard gear, monitors, headphone amps etc. all on one side of the basement AND a "Home Entertainment" system on the other side of the room. I like to switch the playback output of the recording system over to the "Home Entertainment" system to compare mixes and general listening etc. I've had this set up for years and had been dogged by a ground loop hum whenever I switched over to the "Home Entertainment" audio system (lately I've been using a "Mackie BIG KNOB passive" works great!). I tried everything like audio isolation transformers etc. and nothing eliminated the hum.
Last year, I moved everything and was steam cleaning the carpet (yeah, I know it's not the best acoustically but...) and when hooking stuff back up, when the ANTENNA for TV and radio to the receiver was disconnected, the HUM WAS GONE! Bingo, the ground loop was coming from the antenna because I have an 8' copper ground rod driven into the soil and connected to the antenna circuit! I finally found the ground loop!
You all probably won't ever have such an issue but you can see, the more complicated your system, the more places you have to check.
Oh, and if you're wondering how I connected the grounded antenna without the ground loop hum, I connected two 300 to 75 ohm baluns (transformers) back to back going into the receiver and TV and that isolates the ground (if you use baluns that are ground floating).
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Post by Hexspa on Feb 15, 2021 13:40:37 GMT
Ground loops are the worst. I never managed to solve mine. What I did do was get everything to hum the same way. For some reason, when I lift the ground on my mixcube, the noise disappears from all my speakers. Works for me for now.
If I ever get a property I control, one of the first things I'll do is call an electrician to get clean power set up.
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Post by rock on Feb 15, 2021 14:24:19 GMT
Yeah, lifting grounds can do the trick but you loose the safety feature of having the earth ground connection. I believe most if not all residential electrical installations have a "daisy chain" kind of ground as it's more economical. A star grounding is used in studios and were noise reduction is designed into the building. Isolated grounds using a dedicated green wire to earth thereby isolating from the metal conduit take it one step further. It's easier to do from the ground up (NPI) than a "retro-fit" but I imagine it can be done. Using a separate circuit for all your audio is a good start. www.jadelearning.com/blog/the-isolated-ground/ |
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Post by Hexspa on Feb 16, 2021 13:43:53 GMT
Thanks for the clarification, rock. Like many things, I wouldn't know exactly where to start with this. Everything is working fine for now - fingers crossed - but I'll definitely keep this post ready when the time is right.
Cheers.
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